Kidneys are vital organs of the human homeostasis system. Kidneys act as a natural filter in the body which remove toxic metabolic wastes such as urea from the blood. Kidney failure or malfunction may lead to an accumulation of toxins and to an imbalanced electrolyte level in the blood, which may result in undesirable repercussions that are hazardous to an individual's health.
Renal dysfunction and/or failure and, in particular, end-stage renal disease, may cause the body to lose the ability to adequately remove toxic waste in the blood and restore the optimal level of electrolytes in the blood, within physiological ranges. Dialysis is commonly used to replace inadequate kidney function by removing toxic waste.
For the past few years, the predominant form of dialysis used for patients with end-stage renal disease (ESRD) is hemodialysis. Hemodialysis involves the use of an extracorporeal system for the removal of toxins directly from the patient's blood by passing a large amount of the patient's blood through a filtering unit or dialyzer. Hemodialysis treatment typically lasts several hours and must be performed under medical supervision three to four times a week, which significantly decrease a patient's mobility and quality of life. Furthermore, as hemodialysis is performed periodically rather than on a continuous basis, patient health deteriorates as soon as a “treatment cycle” in which contaminants are removed has been completed.
The other form of dialysis used for patients with kidney failure is peritoneal dialysis, most commonly applied in the following two techniques: “continuous ambulatory peritoneal dialysis” (CAPD) and “automated peritoneal dialysis” (APD). In CAPD, fresh dialysate is infused into the patient's abdominal (peritoneal) cavity where, by means of diffusion, metabolic waste and electrolytes in the blood are exchanged with the dialysate across the peritoneal membrane. To allow sufficient diffusion of the electrolytes and metabolic waste to occur, the dialysate is retained in the abdominal (peritoneal) cavity for a couple of hours before removal and replacement (of the spent dialysate) with fresh dialysate. Major drawbacks of continuous ambulatory peritoneal dialysis are a low level of toxin clearance, and the need to continuously replace the spent dialysate, which can be arduous for the patient and disruptive to his/her daily activities.
To address this problem, devices have been designed that reconstitute used/spent dialysate from hemodialysis and/or peritoneal dialysis as opposed to discarding it. However, current devices that reconstitute used/spent dialysate have several associated disadvantages including complex set up procedures and difficulties in maintaining the sterility of components. A further disadvantage is that current devices often require a plurality of fluid connections, which increases the risk of introducing biological contamination and reduces sterility of the device. In addition several components must be disposed of either daily, weekly or monthly adding another layer of complexity to the operation of such devices. In addition, the flow system of known regenerating dialysis devices requires a plurality of pumps, which in turn undesirably increases the overall size, weight and power consumption of the device.
Accordingly, there is a need to provide a dialysis device that overcomes or at least ameliorates one or more of the disadvantages described above. There is also a need to provide a dialysis device without compromising on the size, weight and power consumption of the device.
Furthermore, an ideal artificial kidney should simulate a normal kidney by providing continuous metabolic and fluid control, removal of toxins, and unrestricted patient freedom. As mentioned above, hemodialysis, continuous ambulatory peritoneal dialysis (CAPD), automated peritoneal dialysis (APD) and “24/7” wearable, peritoneal-based artificial kidneys (WAK) are some methods that help renal failure patients to remove metabolic waste. Some of these methods, e.g. the “24/7” wearable, peritoneal-based artificial kidneys (WAK), provide optimal clearance of uremic toxins by continuously regenerating the dialysate using sorbent cartridge technology.
Methods utilizing sorbent cartridge technology typically require a safety mechanism to monitor the exhaustion of the sorbent. Before or when the sorbent is exhausted or does not function well, users need to replace the cartridge to prevent returning toxins back to the patient. One common approach is to monitor the ammonium concentration of the regenerated dialysate to check that it is under a safe level.
However, there are difficulties in dialysis ammonia/ammonium detection. A known method of monitoring the regenerated peritoneal dialysate ammonium concentration in-line is to incorporate an ammonia/ammonium sensor directly onto the dialysate liquid line. In other words, the sensing system is part of the dialysate flow. However, this method requires the ammonia/ammonium sensing system to maintain its sterility at all times, as well as function well. Also, there may be biocompatibility issues. Further, the sensing system has to be compatible with liquid phase applications.
Currently, many liquid phase applications of sensing and monitoring ammonia/ammonium level have their drawbacks and limitations. As such, they are unsuitable for use in peritoneal dialysis.
Besides directly incorporating an ammonia/ammonium sensor in the regenerated dialysate liquid line, it is possible to incorporate a sensor beside the liquid dialysate to monitor the ammonium concentration. For example, US 2007/0161113 A1 and WO 2007/081565 A2 disclose an optical ammonia detecting device where an ammonia sensitive material is placed directly adjacent to a liquid flow path containing regenerated dialysate. The components for the optical detection device are placed adjacent to the ammonia sensitive material, together with the electrical accessories for data processing and signal detection.
However, due to the close proximity of the ammonia sensing material to the hydrophobic membrane, the electrical accessories are disposed very close to the dialysate line. This approach also requires a closed “opaque casing” to prevent any external light interference, which increases manufacturing complexity. Electrical accessories for data processing and signal detection are relatively bulky. Accordingly, miniaturization of portable and wearable peritoneal dialysis devices is difficult. Additional drawbacks of this concept may also include:
Disposable/single use for the ammonia sensing material/part;
Need for patients to assemble the cartridge for use;
Very close/or direct contacting sensor causes potential dialysate leaching leading to a biocompatibility concern; and
Possible improper assembly may cause inaccuracy.
Detection methods and systems disclosed in other publications have several drawbacks such as non-biocompatibility, assembly difficulties (e.g. improper assembly may cause inaccuracies), bulkiness, single-use ammonia sensing components and sterility concerns.
Accordingly, there is also a need to provide a sensing system for detecting ammonium in a dialysate that overcomes or at least ameliorates one or more of the disadvantages described above.